Validity of a two-compartmental model for determination of ascorbate kinetic parameters was assessed by comparing calculated pool sizes derived from specific activity decay curves with chemically determined total body ascorbate. Excellent agreement between the two methods was observed. The technique has been compared to the traditional isotope excretion method and markedly different kinetic parameters are observed. Discrepancies may be accounted for by the stress of confinement of guinea pigs in metabolic chambers and incomplete isotope recovery in isotope excretion experiments. Parameters of ascorbate metabolism, determined by means of compartmental analysis, were greatly influenced by ascorbic acid intake. Half-life of the slowly-miscible pool decreased 56%, pool size increased 7-fold, and turnover rate increased 17-fold as dietary ascorbate was increased from .03 to 5.00 g/kg diet. The kinetic behavior of (1-14C) ascorbic acid was investigated in the whole blood, plasma, and red blood cells (RBC). Ascorbate in RBC's still had not attained equilibrium with plasma ascorbate 7 days after ip. administration. The possibility that this finding could be explained by the rapid entrance of newly ingested ascorbate (as dehydroascorbate) into the RBC's was investigated through administration of an oral dose of (1-14C) ascorbic acid. Since uptake of (1-14C) ascorbate was slower after oral dosing than ip. dosing, this demonstrated that newly ingested ascorbate does not rapidly enter the red blood cell.